C++ MCSymbol::getSection方法代码示例

inline void ARMELFStreamer::SwitchToEHSection(const char *Prefix,
        unsigned Type,
        unsigned Flags,
        SectionKind Kind,
        const MCSymbol &Fn) {
    const MCSectionELF &FnSection =
        static_cast<const MCSectionELF &>(Fn.getSection());

    // Create the name for new section
    StringRef FnSecName(FnSection.getSectionName());
    SmallString<128> EHSecName(Prefix);
    if (FnSecName != ".text") {
        EHSecName += FnSecName;
    }

    // Get .ARM.extab or .ARM.exidx section
    const MCSectionELF *EHSection = NULL;
    if (const MCSymbol *Group = FnSection.getGroup()) {
        EHSection = getContext().getELFSection(
                        EHSecName, Type, Flags | ELF::SHF_GROUP, Kind,
                        FnSection.getEntrySize(), Group->getName());
    } else {
        EHSection = getContext().getELFSection(EHSecName, Type, Flags, Kind);
    }
    assert(EHSection);

    // Switch to .ARM.extab or .ARM.exidx section
    SwitchSection(EHSection);
    EmitCodeAlignment(4, 0);
}

static bool canUseLocalRelocation(const MCSectionMachO &Section,
                                  const MCSymbol &Symbol, unsigned Log2Size) {
    // Debug info sections can use local relocations.
    if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
        return true;

    // Otherwise, only pointer sized relocations are supported.
    if (Log2Size != 3)
        return false;

    // But only if they don't point to a few forbidden sections.
    if (!Symbol.isInSection())
        return true;
    const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
    if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
        return false;

    if (RefSec.getSegmentName() == "__DATA" &&
            RefSec.getSectionName() == "__cfstring")
        return false;

    if (RefSec.getSegmentName() == "__DATA" &&
            RefSec.getSectionName() == "__objc_classrefs")
        return false;

    return true;
}

static bool canUseLocalRelocation(const MCSectionMachO &Section,
                                  const MCSymbol &Symbol, unsigned Log2Size) {
  // Debug info sections can use local relocations.
  if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
    return true;

  // Otherwise, only pointer sized relocations are supported.
  if (Log2Size != 3)
    return false;

  // But only if they don't point to a few forbidden sections.
  if (!Symbol.isInSection())
    return true;
  const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
  if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
    return false;

  if (RefSec.getSegmentName() == "__DATA" &&
      RefSec.getSectionName() == "__objc_classrefs")
    return false;

  // FIXME: ld64 currently handles internal pointer-sized relocations
  // incorrectly (applying the addend twice). We should be able to return true
  // unconditionally by this point when that's fixed.
  return false;
}

bool MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
    const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
    bool InSet, bool IsPCRel) const {
  const MCSection &SecA = SymA.getSection();
  const MCSection &SecB = *FB.getParent();
  // On ELF and COFF  A - B is absolute if A and B are in the same section.
  return &SecA == &SecB;
}

/// EmitValue - Emit label value.
///
void DIELocList::EmitValue(const AsmPrinter *AP, dwarf::Form Form) const {
  DwarfDebug *DD = AP->getDwarfDebug();
  MCSymbol *Label = DD->getDebugLocEntries()[Index].Label;

  if (AP->MAI->doesDwarfUseRelocationsAcrossSections() && !DD->useSplitDwarf())
    AP->emitSectionOffset(Label);
  else
    AP->EmitLabelDifference(Label, Label->getSection().getBeginSymbol(), 4);
}

bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
  // Non-temporary labels should always be visible to the linker.
  if (!Symbol.isTemporary())
    return true;

  // Absolute temporary labels are never visible.
  if (!Symbol.isInSection())
    return false;

  // Otherwise, check if the section requires symbols even for temporary labels.
  return getBackend().doesSectionRequireSymbols(Symbol.getSection());
}

void BTFDebug::beginFunctionImpl(const MachineFunction *MF) {
  auto *SP = MF->getFunction().getSubprogram();
  auto *Unit = SP->getUnit();

  if (Unit->getEmissionKind() == DICompileUnit::NoDebug) {
    SkipInstruction = true;
    return;
  }
  SkipInstruction = false;

  // Collect all types locally referenced in this function.
  // Use RetainedNodes so we can collect all argument names
  // even if the argument is not used.
  std::unordered_map<uint32_t, StringRef> FuncArgNames;
  for (const DINode *DN : SP->getRetainedNodes()) {
    if (const auto *DV = dyn_cast<DILocalVariable>(DN)) {
      visitTypeEntry(DV->getType().resolve());

      // Collect function arguments for subprogram func type.
      uint32_t Arg = DV->getArg();
      if (Arg)
        FuncArgNames[Arg] = DV->getName();
    }
  }

  // Construct subprogram func proto type.
  uint32_t ProtoTypeId;
  visitSubroutineType(SP->getType(), true, FuncArgNames, ProtoTypeId);

  // Construct subprogram func type
  auto FuncTypeEntry =
      llvm::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId);
  uint32_t FuncTypeId = addType(std::move(FuncTypeEntry));

  // Construct funcinfo and the first lineinfo for the function.
  MCSymbol *FuncLabel = Asm->getFunctionBegin();
  BTFFuncInfo FuncInfo;
  FuncInfo.Label = FuncLabel;
  FuncInfo.TypeId = FuncTypeId;
  if (FuncLabel->isInSection()) {
    MCSection &Section = FuncLabel->getSection();
    const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
    assert(SectionELF && "Null section for Function Label");
    SecNameOff = addString(SectionELF->getSectionName());
  } else {
    SecNameOff = addString(".text");
  }
  FuncInfoTable[SecNameOff].push_back(FuncInfo);
}